Boundary of nuclear material sample

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Discussion Overview

The discussion centers around the concept of radioactive decay, specifically addressing the notion of "full life" of a radioactive sample, the decay constant λ, and the implications of these ideas on the understanding of radioactive materials. The scope includes theoretical considerations and mathematical reasoning related to decay processes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that the "full life" of a radioactive sample is infinite, while the life of an individual atom is measurable and short, leading to a contradiction.
  • One participant questions the dimension of the decay constant λ, suggesting it has units of inverse time (sec-1), and relates it to the mean lifetime of decaying species.
  • Another participant challenges the concept of "full life," arguing that it depends on sample size and proposing a definition based on the number of half-lives needed to reach a single atom, estimating it to be approximately 79 half-lives per mole of material.
  • It is noted that radioactive decay is a stochastic process, and while expectation values can be given for decay times, the actual time until all atoms decay is random.

Areas of Agreement / Disagreement

Participants express differing views on the concept of "full life" and its implications, indicating that multiple competing perspectives remain unresolved regarding the nature of radioactive decay and the interpretation of the decay constant.

Contextual Notes

The discussion includes assumptions about definitions of "full life" and the implications of decay constants, which are not universally agreed upon. There are also unresolved mathematical steps related to the decay process and its stochastic nature.

shivakumar06
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we know that the full life of radioactive sample is infinity.
and if we take one radioactive atom in the sample then it's full is measurable and short. it changes when when it emits sub atomic particles. which contradict each other.
we need to know more. the dimension of radioactive constant λ raises an other question.
here N=N0eλt the is on of e so what is the dimension of λ.
 
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shivakumar06 said:
we know that the full life of radioactive sample is infinity.
and if we take one radioactive atom in the sample then it's full is measurable and short. it changes when when it emits sub atomic particles. which contradict each other.
we need to know more. the dimension of radioactive constant λ raises an other question.
here N=N0eλt the is on of e so what is the dimension of λ.

λ is the decay constant with units if inverse time. If time t is in seconds, then λ is sec-1.

N(t) = N0 exp(-λt)

The decay constant is also the inverse of the mean lifetime of the decaying species.
 
shivakumar06 said:
we know that the full life of radioactive sample is infinity.
and if we take one radioactive atom in the sample then it's full is measurable and short. it changes when when it emits sub atomic particles. which contradict each other.
we need to know more. the dimension of radioactive constant λ raises an other question.
here N=N0eλt the is on of e so what is the dimension of λ.

There is no such thing as "full life", as such a quantity would depend on the sample size and not the properties of the material. But if you wanted to, you could define the "full-life" of a sample as the number of half lives required before you are left with a single atom. This "full-life" would not be infinity, in fact the value would be equal to approximately 79 half lives per mol of material (Na/2^79 ~= 1).
 
Radioactive decay is a stochastic process (at least for all observers). You can give an expectation value (and a distribution function) for the time until all atoms decayed, but the time in an experiment will be random.
 

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